关键词: 前臼齿; 齿冠形状; 几何形态测量; 现代中国人

Abstract: This study analyzes the outline and polygon shapes of maxillary and mandibular premolars of recent Chinese collected from archeological sites at Xichuan, Henan Province, and from Yunxian, Dan Jiang Kou, Hubei Province. The following conclusions from this research have been made. The outline of P1 is symmetrical with the buccal part extending mesially and distally; its polygon shape is an irregular rhombus with the lingual tip moving mesially. The outline of P2 is also symmetrical, and the extent to which the buccal part extends mesially and distally varies among individual teech; its polygon shape is an irregular rhombus due mainly to the mesially displaced lingual tip. The mesiolingual edge of P1 contracts inside, which makes its outline asymmetrical as a whole; its polygon approaches the mesiolingual edge of the outline, with its shape being similar to a square. The P2 possesses a centered occlusal polygon, irregular rhombus in shape but with a basically symmetrical outline. Both shapes of the outline and polygon overlap little between P1 and P2. The extent of variation extent and manner of both the outline and the polygon collectively resembles each other between P1 and P2 . The P1could be sorted into two categories on the basis of the distance between the tip of the buccal cusp and its neighboring edge of outline. Based on the extent of the buccal part of the outline there could be two groupings of P2 . Tooth variations are greater in the mandibular premolars compared to their maxillary counterparts, with differences found mainly in the distolingual part of the outline, distal fovea, and the tip of the lingual cusp. Three types of P1 or P2 could be attained when cousidering the proportion of buccolingual and mesiodistal distances, locality of distal fovea, and the lingual cusp tip. Allometric analysis indicates that the shapes of all four premolars are not obviously impacted by their sizes.

Key words: Premolar; Shape; Geometric morphometrics; Recent Chinese population